Telecommunication networks increasingly use the Optical Transport Network (OTN) standards for aggregation and transport of Ethernet data traffic. The standard method of mapping Ethernet frames to optical transport unit (OTUk) frames involves terminating the packets and mapping them using generic framing protocol frames (GFP-F). However, GFP-F does not provide synchronization between the timing of the Ethernet network and the timing of the OTN. Consequently, telecommunications providers must add extra equipment to add stratum timing at the egress of the telecommunications network, resulting in increased equipment and operating costs. Further, adding stratum synchronized timing from an external source requires meeting stringent timing wander requirements. Addressing these wander requirements requires complicated and expensive stratum synchronization circuits.
For synchronous 10 Gigabit Ethernet (10GBE), there are transparent timing mappings to over-clocked OTU2x, (such as, for example, OTU1e, at 11.05 Gigabits per second (Gb/s) and OTU2e at 11.09 Gb/s.) These over-clocked signals cannot be passed over a standard OTU2 link or multiplexed into a standard OTU3 link.
Therefore, there is a need for synchronization between an Ethernet link and an OTN link that provides a transparent timing change at a boundary node between the links.